Abstract
Water stress is likely the most important factor that adversely affects plant growth and development. In our study two inbred lines of sunflower (Helianthus annuus L.) with contrasting behavior to water deficit, the inbred lines B59, sensitive, and B71, tolerant, were subjected to water stress and compared in terms of growth parameters, relative water content, photosynthetic pigments and osmo-compatibles contents. Mannitol treatment generated a moderate water stress which resulted in a relative water content decline in both lines. In aerial part of B59 and B71 stressed-seedlings, a dramatic reduction of osmotic potential was observed, although in B71 the osmotic potential was 1.8-fold lower than in B59. The B71 line recovered the osmotic potential to control values after 8 d of re-watering. Several morphological parameters were altered by the water stress. Shoot and root relative fresh weight decreased in both lines under water stress, although B71 showed a minor drop. However, the root was less affected than the shoot in stress condition and recovery period. Water stress was affected in a greater proportion shoot dry weight (DW) than root DW in B59 and B71 lines. Nevertheless, a significant increase in root DW/shoot DW ratio was observed in stressed seedlings. A higher reduction in the individual leaf area was observed in B71 line under stress. The basal chlorophyll content was higher in the tolerant line B71 than in the sensitive B59, and carotenoids showed a high content in B71 control and stressed seedlings. Under water stress, the aerial and root proline content increased in the tolerant B71 line. Glycinebetaine decreased significantly in the aerial part of both lines in response to water stress indicating that this compound is not the main osmo-regulator. In conclusion, B71 has suitable mechanisms to enable it to respond more effectively to moderate water stress.
Highlights
Water stress is one of the most important factors of abiotic stresses that affect on growth and yield of plants worldwide [1,2]
We investigated to what extent moderate water stress affects growth parameters, relative water content (RWC), photosynthetic pigments and osmo-compatibles contents in two sunflower lines of contrasting behavior to water deficit
No significant differences were observed between both lines, but water stress significantly decreased leaf RWC, and the reduction was almost the same for the two lines
Summary
Water stress is one of the most important factors of abiotic stresses that affect on growth and yield of plants worldwide [1,2]. A drop in water potential induces a variety of metabolic, morphological, and/or physiological responses, including reduction in the vegetative growth [3], generation of eactive oxygen species [4], accumulation of osmotically active solutes [5], changes in endogenous levels of plant hormones [6,7,8], and altered expression of stress responsive-genes [9,10,11]. In sunflower (Helianthus annuus L.), low water availability in the soil has a negative impact on yield, which depends on the plant ontogenetic stage for which this occurs. This crop is better able to tolerate drought than many agricultural crop species, and is often cultivated in arid regions. Like other oil crops, sunflower is sensitive to water deficit at the germination stage [14]
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